TCP IP Illustrated

Timeticks a counter that counts the time in

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Unformatted text preview: st, since the values are being queried, not set. lpAddress. An OCTET STRING of length 4, with 1 byte for each byte of the IP address. PhysAddress. An OCTET STRING specifying a physical address (e.g., a 6-byte Ethernet address). file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/snmp_sim.htm (4 of 33) [12/09/2001 14.47.40] Chapter 25. SNMP: Simple Network Management Protocol q q q q q Counter. A nonnegative integer whose value increases monotonically from 0 to 232-1 (4,294,967,295), and then wraps back to 0. Gauge. A nonnegative integer between 0 and 232 -1, whose value can increase or decrease, but latches at its maximum value. That is, if the value increments to 232 - 1, it stays there until reset. The MIB variable tcpCurrEstab is an example: it is the number of TCP connections currently in the ESTABLISHED or CLOSE_WAIT state. TimeTicks. A counter that counts the time in hundredths of a second since some epoch. Different variables can specify this counter from a different epoch, so the epoch used for each variable of this type is specified when the variable is declared in the MIB. For example, the variable sysUpTime is the number of hundredths of a second that the agent has been up. SEQUENCE. This is similar to a structure in the C programming language. For example, we'll see that the MIB defines a SEQUENCE named UdpEntry containing information about an agent's active UDP end points. (By "active" we mean ports currently in use by an application.) Two entries are in the structure: 1. udpLocalAddress, of type lpAddress, containing the local IP address. 2. udpLocalPort, of type INTEGER, in the range 0 through 65535, specifying the local port number. SEQUENCE OF. This is the definition of a vector, with all elements having the same data type. If each element has a simple data type, such as an integer, then we have a simple vector (a one-dimensional array). But we'll see that SNMP uses this data type with each element of the vector being a SEQUENCE (structure). We can then thi...
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